Sucker rod

ABSTRACT

A sucker rod, including: a rod; a threaded casing disposed outside the rod; a wedge-shaped groove disposed at one end of the rod; an outer connecting screw thread close to the wedge-shaped groove and disposed outside the rod; a wedge-shaped bulge disposed at the other end of the rod; a positioning nut close to the wedge-shaped bulge and matching with the threaded casing and disposed outside the rod; an inner nut flexibly disposed outside the rod between the positioning nut and the wedge-shaped bulge; and an outer nut flexibly disposed outside the rod for cooperation with the threaded casing; a convex plate disposed inside one end of the threaded casing for cooperation with the positioning nut; and an inner connecting screw thread disposed at the other end of the threaded casing for cooperation with the outer connecting screw thread. The sucker rod has a high torsional strength and is stable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/CN2010/000846 with an international filing date of Jun. 12,2010, designating the United States, now pending. The contents of all ofthe aforementioned applications, including any intervening amendmentsthereto, are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a sucker rod used in oil wells of oil fields,and more particularly to a special plug-in sucker rod for driving screwpumps.

2. Description of the Related Art

Conventional sucker rods for driving screw pumps in oil fields includecommon sucker rods and those having a fan-shaped head. Two common suckerrods are connected using a joint hoop. One end of the joint hoop isconnected using threads with one end of a sucker rod, and the other endof the joint hoop is connected using threads with one end of anothersucker rod. Because the connection employs a straight thread, the suckerrod has a low torsional strength and is mainly used in pumpingproduction wells in a reciprocating linear motion. When sucker rodshaving a fan-shaped head rotate in a screw pump well, the connectionbetween the joint hoops and the sucker rods easily loosens and thusaccident happens, thereby reducing the work efficiency of screw pumps.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is one objective of theinvention to provide a special plug-in sucker rod for screw pumps thathas a high torsional strength and is difficult to break off.

To achieve the above objective, in accordance with one embodiment of theinvention, there is provided a special plug-in sucker rod for screwpumps comprising a rod and a threaded casing disposed outside the rod,wherein a wedge-shaped groove is disposed at one end of the rod, and anouter connecting screw thread close to the wedge-shaped groove isdisposed outside the rod; a wedge-shaped bulge is disposed at the otherend of the rod, and a positioning nut close to the wedge-shaped bulgeand matching with the threaded casing is disposed outside the rod usinga flexible connection.

To further prevent the breaking off of the sucker rod, an inner nut isdisposed outside the rod using a flexible connection between thepositioning nut and the wedge-shaped bulge. Thus, the threaded casing isstably fixed in the axial direction via the positioning nut and theinner nut.

An outer nut is disposed outside the rod using a flexible connection forcooperation with the threaded casing. The threaded casing is furtherfixed in the axial direction with the help of the outer nut.

A convex plate is disposed inside one end of the threaded casing forcooperation with the positioning nut, and the other end of the threadedcasing is provided with an inner connecting screw thread. The innerconnecting screw thread matches with an outer connecting screw thread ofone end of another sucker rod. Thus, two sucker rods are connected viathe threaded casing which is fixed in the axial direction via thepositioning nut.

The flexible connection is a threaded connection, which is convenientfor disassembly.

Advantages of the invention are summarized below. The special plug-insucker rod of screw pumps comprises the rod and the threaded casingdisposed outside the rod. The wedge-shaped groove is disposed at one endof the rod, and the outer connecting screw thread close to thewedge-shaped groove is disposed outside the rod. The wedge-shaped bulgeis disposed at the other end of the rod, and the positioning nut closeto the wedge-shaped bulge and matching with the threaded casing isdisposed outside the rod using a flexible connection. The match of thewedge-shaped groove of the sucker rod with the wedge-shaped bulge ofanother sucker rod achieves the plug-in match of two sucker rods. Theconnection part of the two sucker rods is surrounded by the threadedcasing which fixes the two sucker rods in the axial direction. Theconnection structure can bear a large torque, thereby improving thetorsional strength of the sucker rod in screw pump wells. Furthermore,the positioning nut, the inner nut, and the outer nut further make thethreaded casing fixed in the axial direction. Thus, the sucker rod willnot loosen and break off, accidents are avoided, work efficiencyimproved, and the production cost reduced. Therefore, compared with theexisting technology, the invention has a prominent substantive featureand notable progress, and the beneficial effect is obvious.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structure diagram of a sucker rod according to oneembodiment of the invention; and

FIG. 2 is an assembly diagram of two sucker rods according to oneembodiment of the invention.

In the drawings, the following reference numbers are used: 1.Wedge-shaped groove; 2. Outer connecting screw thread; 3. Rod; 4. Outernut; 5. Convex plate; 6. Positioning nut; 7. Inner nut; 8. Wedge-shapedbulge; 9. Threaded casing; 10. Inner connecting screw thread.

DETAILED DESCRIPTION OF THE EMBODIMENTS

For further illustrating the invention, experiments detailing a suckerrod are described below. It should be noted that the following examplesare intended to describe and not to limit the invention.

As shown in FIG. 1, a special plug-in sucker rod of screw pumpscomprises a rod 3 and a threaded casing 9 outside the rod 3. Awedge-shaped groove 1 is disposed at one end of the rod 3. An outerconnecting screw thread 2 close to the wedge-shaped groove 1 is disposedat one end of the rod 3. A wedge-shaped bulge 8 is disposed at the otherend of the rod 3, and a positioning nut 6 close to the wedge-shapedbulge 8 and matching with the threaded casing 9 is disposed using aflexible connection (for example, threaded connection) outside the rod3. An inner nut 7 is disposed using a flexible connection (for example,threaded connection) outside the rod 3 between the positioning nut 6 andthe wedge-shaped bulge 8. An outer nut 4 is disposed using a flexibleconnection (for example, threaded connection) outside the rod 3 forcooperation with the threaded casing 9. A convex plate 5 is disposedinside one end of the threaded casing 9 for cooperation with thepositioning nut 5, and the other end of the threaded casing is providedwith an inner connecting screw thread 10 for matching with an outerconnecting screw thread 2 of one end of another sucker rod 3.

Assembly process: as shown in FIG. 1 and FIG. 2, first, the outer nut 4is disposed outside the rod 3 of the sucker rod, and then the threadedcasing 9 is disposed. The positioning nut 6 and the inner nut 7 arescrewed in turn. The match of the positioning nut 6 and the convex plate5 of the threaded casing 9 fixes the threaded casing 9 in the axialdirection. Thereafter, the wedge-shaped bulge 8 of the rod 3 is pluggedinto the wedge-shaped groove 1 of the rod 3 of another sucker rod, toachieve the connection of two sucker rods by the connection of thethreaded casing 9 and the outer connecting screw thread 2 of the rod 3of the sucker rod with the wedge-shaped groove 1. Finally, the outer nut4 is tightened. With the cooperation of the positioning nut 6, the innernut 7, and the outer nut 4, the threaded casing 9 is firmly fixed in theaxial direction and thus the two sucker rods are connected. Theconnection mode can effectively improve the torsional strength of thesucker rod. The number of the sucker rod is determined by actual needs,and thus a sucker rod pole is formed by a plurality ofsequentially-connected sucker rods.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention inits broader aspects, and therefore, the aim in the appended claims is tocover all such changes and modifications as fall within the true spiritand scope of the invention.

1. A sucker rod, comprising: a) a rod; b) a threaded casing disposedoutside the rod; c) a wedge-shaped groove; d) an outer connecting screwthread; e) a wedge-shaped bulge; and f) a positioning nut; wherein thewedge-shaped groove is disposed at one end of the rod, and the outerconnecting screw thread close to the wedge-shaped groove is disposedoutside the rod; and the wedge-shaped bulge is disposed at the other endof the rod, and a positioning nut close to the wedge-shaped bulge andmatching with the threaded casing is disposed outside the rod using aflexible connection.
 2. The sucker rod of claim 1, wherein an inner nutis disposed outside the rod using a flexible connection between thepositioning nut and the wedge-shaped bulge.
 3. The sucker rod of claim1, wherein an outer nut is disposed outside the rod using a flexibleconnection for cooperation with the threaded casing.
 4. The sucker rodof claim 2, wherein an outer nut is disposed outside the rod using aflexible connection for cooperation with the threaded casing.
 5. Thesucker rod of claim 3, wherein a convex plate is disposed inside one endof the threaded casing for cooperation with the positioning nut, and theother end of the threaded casing is provided with an inner connectingscrew thread.
 6. The sucker rod of claim 4, wherein a convex plate isdisposed inside one end of the threaded casing for cooperation with thepositioning nut, and the other end of the threaded casing is providedwith an inner connecting screw thread.
 7. The sucker rod of claim 5,wherein the flexible connection is a threaded connection.
 8. The suckerrod of claim 6, wherein the flexible connection is a threadedconnection.